SkPDF:  minor cleanups of skpdfdevice

Change-Id: I2143daaa6061003d8631f38ea39724fb12d494db
Reviewed-on: https://skia-review.googlesource.com/24747
Reviewed-by: Ben Wagner <bungeman@google.com>
Commit-Queue: Hal Canary <halcanary@google.com>
diff --git a/src/pdf/SkPDFDevice.h b/src/pdf/SkPDFDevice.h
index 6df9d6d..51a9b10 100644
--- a/src/pdf/SkPDFDevice.h
+++ b/src/pdf/SkPDFDevice.h
@@ -132,6 +132,8 @@
 
     SkPDFCanon* getCanon() const;
 
+    SkIRect bounds() const { return this->imageInfo().bounds(); }
+
     // It is important to not confuse GraphicStateEntry with SkPDFGraphicState, the
     // later being our representation of an object in the PDF file.
     struct GraphicStateEntry {